This invention relates generally to a cartridge or a casing for containing an information recording disc, such as a video and/or audio disc, and more particularly, the present invention relates to the structure of a lock arm provided to a detachable lid of such a disc cartridge.
Various types of information recording discs carrying video and/or audio signals are known. Although discs of the type arranged to be treated without being covered by a suitable container are known, there is another type of discs which are contained in a suitable container. Each container contains a single disc therein, and is inserted into a reproducing apparatus or player so that only the disc is left in the apparatus and the container is pushed out. In order that the disc kept in the container is taken out within the reproducing apparatus, the container has an opening at one end which is covered by a detachable lid. Since the disc container is inserted into the reproducing apparatus to place the disc at a given position in the apparatus, the container is referred to as a disc cartridge. After playback, the empty cartridge is again inserted into the reproducing apparatus so that the disc is again kept in the cartridge, and then the cartridge is taken out either automatically or manually.
In order that the disc in the cartridge inserted into the reproducing apparatus is automatically taken out of the cartridge, the lid of the cartridge has two lock arms at both ends thereof. Each of the lock arms has a projection arranged to engage a recess provided to the cartridge body so that the lid is normally connected to the cartridge body. When the cartridge is inserted into the reproducing apparatus, the lock arm is pressed by a stationary member in the reproducing apparatus to disengage from the recess. Thus the lid is separated from the cartridge body, and then the cartridge body is pressed backward with the disc being held by a suitable supporting member of the reproducing apparatus. As a result, the lid and the disc remain in the reproducing apparatus, while the cartridge body is ejected.
Both the cartridge body and the lid are made of a synthetic resin. Although it is preferable that the lock arms provided to the lid are also made of the same synthetic resin to be integral with the lid body in view of cost reduction, it has been difficult to integrally form the lock arms with the lid body because of the following reasons. When each of the lock arms is made of a synthetic resin, the lock arm has a given shape to show elasticity so that it moves between two positions for engagement and disengagement. However, since the cartridge is loaded and unloaded many times or when the lock arm is continuously compressed for a long period of time in the reproducing apparatus, the elasticity or characteristic of spring of the lock arm is apt to deteriorate. Furthermore, application of heavy stress is apt to result in permanent strain and/or blushing, i.e. a phenomena in which a portion of the synthetic resin turns white due to application of stress beyond the limit of elasticity.
If the lock arm does not return to its original position, the projection thereof is difficult to engage the recess of the cartridge body, resulting in a problem that only the cartridge body is ejected leaving the lid in the reproducing apparatus with the disc being particially received in the cartridge body even if it is intended to eject the lid together with the cartridge body after playback. For this reason, the lock arms are made of metallic leaf springs in known disc cartridges. Namely, a pair of lock arms each made of a leaf spring, are attached to given positions of the lid body. However, it is time-consuming and troublesome to attach such metallic lock arms to the lid body.